WaistLine Underbust Trainer Belt

Core support that keeps up with your workout, not just your outfit. WaistLine wraps your midsection in breathable, flexible compression so you feel held together through every rep.

Why you'll love it:

Breathable nylon-spandex mesh moves with you instead of against you
Hook-and-eye closure adjusts as you do, set after set
Wear it under everyday clothes or layered over activewear at the gym
Flexible boning supports your core without locking you in place

Fit: Measure your natural waist before ordering for the most accurate fit.

Free US shipping. 30-day returns.

Size Guide

Use this guide to find your size across our shapewear, corsets, and waist trainers. Letter sizes are matched to standard US dress sizes below — if you're between two sizes, size up for all-day comfort or size down for maximum compression.

Corsets, Bustiers & Body Shapers

Size	US Dress Size	Waist (in)	Hip (in)
S	4–6	25–27	35–37
M	8–10	28–30	38–40
L	12–14	31–33	41–43
XL	16–18	34–37	44–47
XXL / 2XL	20–22	38–41	48–51
XXXL / 3XL	24–26	42–45	52–55
4XL	28–30	46–49	56–59
5XL	32–34	50–53	60–63
6XL	36–38	54–57	64–67

Waist Trainers & Waist Belts

Size	Natural Waist (in)
XS	23–25
S	26–28
M	29–31
L	32–35
XL	36–39
XXL	40–43
XXXL	44–47
4XL	48–51

Leggings & High-Waist Briefs

Size	US Dress Size	Waist (in)	Hip (in)
S	2–4	24–26	34–36
M	6–8	27–29	37–39
L	10–12	30–32	40–42
XL	14–16	33–36	43–46

How to Measure

Waist: Measure around your natural waistline, at the narrowest point above your belly button.
Hip: Measure around the fullest part of your hips, keeping the tape parallel to the floor.

This chart is a general US sizing reference across our shapewear styles. Exact fit can vary slightly by garment and material stretch — check the size note on each product page for style-specific guidance.